fix(payment): wire balance wallet end-to-end when pay_balance_s is on

Opening 余额功能 alone now enables cash-wallet pay (unless 余额支付 is explicitly off). Drop points-as-balance fallback, stop fake method injection, expose real wallet in cashiers, and honor auto_to_balance on recharge fulfill.

inc/helpers/aksrt-pay.php

@@ -107,12 +107,8 @@ if (!function_exists('aksrt_list_cash_payment_methods')) {
             ];
         }
 
-        if ($methods === []) {
-            $methods[] = $logged_in
-                ? ['id' => 'balance', 'name' => __('站内余额', 'aksrt')]
-                : ['id' => 'alipay', 'name' => __('支付宝', 'aksrt')];
-        }
-
+        // Do not inject a fake balance/alipay option when nothing is configured —
+        // callers should surface “暂无可用支付方式” instead of a dead method.
         return $methods;
     }
 }